High frequency circuit applications (e.g., ASIC high speed serial (HSS) links, power amplifiers in wireless communications, etc.) require low-capacitance electrostatic discharge (ESD) protection. For example, a power amplifier in CMOS technologies is susceptible to ESD events, which can damage the integrated circuit (IC), hence requiring ESD protection.
Conventional ESD devices using, e.g., ESD diodes, ESD NFETs, etc., tend to have a high parasitic capacitance which impacts circuitry when the ESD is off, during normal operation. Silicon-Controlled-Rectifier (SCR) structures are a desired alternative ESD structure because they offer both low capacitance and high ESD performance compared to, for example, ESD diodes and ESD NFETs. An SCR device is a four layer solid-state current-controlling device. The four layer device includes p-n-p-n layers forming a PNPN structure or n-p-n-p layers forming an NPNP structure, either of which have three P-N junctions and three terminals. SCRs are unidirectional devices (i.e., can conduct current only in one direction) and can be triggered normally only by currents going into the gate (as opposed to TRIACs, which can be triggered normally by either a positive or a negative current applied to its gate electrode).